1. Field of the Invention
The invention relates to an axle assembly for a non-powered axle of a commercial vehicle, comprising an axle produced from a first metal material and at least one trailing link which is produced from a second metal material and has a connecting portion with a seat in which the axle sits with a hollow coupling portion such that the axle and the trailing link are torque-proof engaged with one another. Axle assemblies of this type are used, for example, on trailers or semi-trailers for lorries and articulated lorries.
2. Description of the Related Art
There are many known axle constructions of this type which are also termed “rigid axles”. They usually comprise a trailing link which is coupled pivotally by one end to the vehicle frame via a suitable joint and is supported on the other side on the vehicle via a spring/damper combination. This allows a simple resilient mounting of an axle which meets the requirements made hitherto for trailers or semi-trailers of lorries, for example. The travelling behaviour of axle assemblies of the type in question can be improved by designing the axle such that at least portions of it are torsionally flexible, so that the movements of the trailing links bearing the axle are uncoupled from one another to a greater extent.
As summarised in EP 0 830 959 B1 or in DE 10 2006 009 441 A1, the connection between the trailing links and the axle supported thereby is produced in the prior art by clamping, screwing or welding, for example. In this respect, the trailing links are usually made of cast steel, whereas the axles are produced as profiles from a steel material.
A disadvantage of the known axle constructions described above is that they usually require a high material and production expense so that particularly the mounting thereof in the trailing links can absorb the high stresses which occur in practice with sufficient reliability.
Another axle assembly of the type stated above is known from EP 0 713 791 B1. In a first variant of the axle assembly described in this document, a trailing link is used which is configured as a hollow aluminium profile and is closed at its ends. Configured on one end thereof by a forming process also termed “hydroforming” is a head part which is subsequently provided with a passage opening oriented transversely to the longitudinal extent of the trailing link.
In “hydroforming” of the type described in EP 0 713 791 B1, the hollow component to be formed is introduced into a die presenting the desired shape of the component and then subjected from inside to a high-pressure incompressible fluid. Thereupon, the material of the trailing link starts to flow until it lies against the inner surfaces of the die. Thus, it is possible to configure with high precision on prefabricated profiles specific moulded elements which are required for the further operation of the component to be respectively produced.
In order to produce the passage opening in the head part produced by hydroforming, of the trailing link, in the prior art described in EP 0 713 791 B1 the wall material, present in the region intended for said passage opening, of the trailing link is removed by a machining process. The shape of the opening cross-section differs from that of a circle. Subsequently, inserted through the opening in the trailing link is an axle, the external dimensions of which are adapted to the shape of the opening of the trailing link such that after being inserted, the axle sits positively and non-rotatably in the opening in the trailing link.
Since the head part is then compressed by an externally acting pinching tool, according to EP 0 713 791 B1, the positive locking can be optimised between the axle and the trailing link. This same purpose is served when it is proposed in EP 0 713 791 B1 to widen the axle seated in the trailing link by hydroforming.
It is likewise possible according to EP 0 713 791 B1 to secure the torque-proof engagement between the trailing link and the axle by also connecting them together in a material-uniting manner by bonding or welding or additionally in a non-positive and positive manner by mechanical processes, such as clinching.
Finally, according to EP 0 713 791 B1, hydroforming can respectively form the end portions of the axle which respectively freely project beyond the trailing link such that they can be used for connecting a wheel support plate or as a seat for a rubber joint of a spring system.
The variants of the prior art described in EP 0 713 791 B1, in which hydroforming is used, each proceed from axles and trailing links which are produced as extruded profiles of an aluminium material of the composition also stated in EP 0 713 791 B1. An additional variant of the prior art described in EP 0 713 791 B1 provides the prefabrication of the trailing link as a cast part, on which a seat for the axle is already configured, which seat differs from a circular shape. The correspondingly formed axle is then introduced into the seat of the trailing link. The cross-sectional shape of axle and trailing link seat which differs from a circle ensures that the axle is mounted in the seat with no risk of twisting. The actual connection between trailing link and axle according to EP 0 713 791 B1 is then made by bonding, welding or shrinking.
The advantage of the various configuration variants of an axle assembly known from EP 0 713 791 B1 is that they allow, in a relatively simple manner, the axle to be formed and attached such that on the one hand it has a torsionally flexible centre portion which can be used in the manner of a torsion spring, while on the other hand it is held securely in the trailing links by its coupling portions respectively associated with the trailing links.
These advantages are countered by the disadvantage that in spite of the use of modern production methods, such as hydroforming, the production of the known assembly is expensive. Furthermore, an axle assembly produced according to EP 0 713 791 B1 is incapable of absorbing with sufficient reliability the high stresses which occur in the practical use of a commercial vehicle.